The present invention relates to a system for opening the frangible bottom of a cylindrical cartridge moulded from degradable plastics material more particularly intended for pasty products such as greases or the like.
Cartridges of such pasty products are already known, which comprise a tubular body closed, at one of its ends, by a bottom moulded with the lateral wall of the body and, at its other end, by a removable cap obturating the outlet orifice of the cartridge. Such cartridges are intended to be used with apparatus such as dispenser guns. To that end, the user previously tears off the bottom of the cartridge to allow the introduction through the passage thus formed of a piston delivering towards the outlet orifice the pasty product contained in the cartridge.
The necessary recycling of the material used for the manufacture of such cartridges has led to replacing the PVC by biodegradable products such as polyethylene; in the same way as the PVC formerly used for the cartridges was easily cut in order to open the bottom, polyethylene does not lend itself easily to the cut-outs of the bottom made with current blunt objects. One has therefore been rapidly led to seeking solutions for easy opening of the bottoms of polyethylene cartridges, which remain economically acceptable.
To this end, a solution has already been proposed by Applicant in his French Patent FR 2 709 732 in which the bottom of the grease cartridge is linked to the wall of the tubular body of said cartridge by a connection zone of lesser resistance so that its separation from the tubular body at the moment of use thereof in a dispenser gun procures a neat passage through which can be engaged the piston of the gun which ensures delivery of the grease outside the cartridge. According to this Patent, the bottom of the cartridge is constituted by a band extending spirally and flat from a central point, the turns being contiguous and joined by a line of lesser resistance, so that, by pulling at the centre of the bottom of the cartridge by means of a gripping member, the bottom of the cartridge is progressively cut open. Although such a device is particularly adapted to degradable materials such as polyethylene, it nonetheless presents numerous drawbacks: the cartridge is opened by successive jerks when the successive turns are detached and, in addition, the spirally wound ribbon thus obtained is torn all at once from the periphery of the tubular body of the cartridge, which has the unpleasant effect of projecting, at the moment of release of the band which then behaves like a spring, the residual grease present on that face of the spiral which was in contact with the grease before opening.
The present invention has for an object to contribute a clear improvement to this system of frangible opening of a cylindrical cartridge for pasty product or the like, moulded from a plastics material and adapted to be used in a dispenser gun incorporating piston as tubular body, to ensure, in cooperation with said piston the progressive delivery of the pasty product through one or the ends of said cartridge normally obturated before use by a cap, the other end of the tubular body being, before use, closed by a frangible lid moulded with the lateral wall of the body and of which the detachment by a pull ring procures, as in the prior art cited, a neat passage ensuring free circulation of the product delivered by the piston.
According to the invention, this cylindrical cartridge is noteworthy in that the lid which has the general shape of a disc which is substantially planar at least on its inner face, surrounded by a vertical skirt which extends from and above its outer face, over a constant height, substantially perpendicular to the plane of the disc, is secured to the inner face of the corresponding end of the tubular body or of the piece which acts as such, by a tearaway film made of moulded matter linking it to the outer face of the upper end of the skirt, the latter comprising at a point of its circumference a vertical cut over the whole of its height extending horizontally on the disc over a substantially equal distance to form a radial cutout of which the banks support two substantially equal vertical flanks, preferably parallellepipedic and disposed opposite each other, of thickness at least equal to that of the skirt and of the same height, secured vertically to the banks of the vertical cut and linked together by their opposite outer free edges by a tearaway film of moulded matter forming the seal of the lid, a thread of moulded matter of appropriate shape emerging from the outer face of one of the flanks, on the side located opposite its attachment to the skirt in order to be secured symmetrically on the other side to the outer face of the other flank to form the outer pull ring.
The interest of this new solution will be readily understood, whereby the flat cut-out band proposed in the prior art is replaced by a simple detachable lid provided with an adequate cutout making it possible to create a zone of privileged upward bending of the detachable part of the lid concentrating the efforts of pull at the level of said cutout, which provokes tear at that precise point and then allows a progressive detachment on either side of the cutout, thus limiting, if not avoiding, the spring effect feared in the prior art.
This solution is particularly advantageous since it makes it possible, for the same effort, to obtain detachment of the lid more easily by concentrating all the effort at the same point instead of distributing it over a broad sector of angle of the lid, as known on the majority of previously known frangible openings.